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331 lines
12 KiB
C++
331 lines
12 KiB
C++
/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "ImageScaling.h"
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#include "mozilla/Attributes.h"
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#include "SSEHelpers.h"
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/* The functions below use the following system for averaging 4 pixels:
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*
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* The first observation is that a half-adder is implemented as follows:
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* R = S + 2C or in the case of a and b (a ^ b) + ((a & b) << 1);
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*
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* This can be trivially extended to three pixels by observaring that when
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* doing (a ^ b ^ c) as the sum, the carry is simply the bitwise-or of the
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* carries of the individual numbers, since the sum of 3 bits can only ever
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* have a carry of one.
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*
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* We then observe that the average is then ((carry << 1) + sum) >> 1, or,
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* assuming eliminating overflows and underflows, carry + (sum >> 1).
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*
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* We now average our existing sum with the fourth number, so we get:
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* sum2 = (sum + d) >> 1 or (sum >> 1) + (d >> 1).
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*
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* We now observe that our sum has been moved into place relative to the
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* carry, so we can now average with the carry to get the final 4 input
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* average: avg = (sum2 + carry) >> 1;
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*
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* Or to reverse the proof:
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* avg = ((sum >> 1) + carry + d >> 1) >> 1
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* avg = ((a + b + c) >> 1 + d >> 1) >> 1
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* avg = ((a + b + c + d) >> 2)
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*
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* An additional fact used in the SSE versions is the concept that we can
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* trivially convert a rounded average to a truncated average:
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*
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* We have:
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* f(a, b) = (a + b + 1) >> 1
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*
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* And want:
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* g(a, b) = (a + b) >> 1
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*
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* Observe:
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* ~f(~a, ~b) == ~((~a + ~b + 1) >> 1)
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* == ~((-a - 1 + -b - 1 + 1) >> 1)
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* == ~((-a - 1 + -b) >> 1)
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* == ~((-(a + b) - 1) >> 1)
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* == ~((~(a + b)) >> 1)
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* == (a + b) >> 1
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* == g(a, b)
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*/
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MOZ_ALWAYS_INLINE __m128i _mm_not_si128(__m128i arg)
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{
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__m128i minusone = _mm_set1_epi32(0xffffffff);
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return _mm_xor_si128(arg, minusone);
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}
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/* We have to pass pointers here, MSVC does not allow passing more than 3
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* __m128i arguments on the stack. And it does not allow 16-byte aligned
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* stack variables. This inlines properly on MSVC 2010. It does -not- inline
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* with just the inline directive.
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*/
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MOZ_ALWAYS_INLINE __m128i avg_sse2_8x2(__m128i *a, __m128i *b, __m128i *c, __m128i *d)
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{
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#define shuf1 _MM_SHUFFLE(2, 0, 2, 0)
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#define shuf2 _MM_SHUFFLE(3, 1, 3, 1)
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// This cannot be an inline function as the __Imm argument to _mm_shuffle_ps
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// needs to be a compile time constant.
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#define shuffle_si128(arga, argb, imm) \
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_mm_castps_si128(_mm_shuffle_ps(_mm_castsi128_ps((arga)), _mm_castsi128_ps((argb)), (imm)));
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__m128i t = shuffle_si128(*a, *b, shuf1);
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*b = shuffle_si128(*a, *b, shuf2);
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*a = t;
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t = shuffle_si128(*c, *d, shuf1);
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*d = shuffle_si128(*c, *d, shuf2);
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*c = t;
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#undef shuf1
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#undef shuf2
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#undef shuffle_si128
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__m128i sum = _mm_xor_si128(*a, _mm_xor_si128(*b, *c));
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__m128i carry = _mm_or_si128(_mm_and_si128(*a, *b), _mm_or_si128(_mm_and_si128(*a, *c), _mm_and_si128(*b, *c)));
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sum = _mm_avg_epu8(_mm_not_si128(sum), _mm_not_si128(*d));
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return _mm_not_si128(_mm_avg_epu8(sum, _mm_not_si128(carry)));
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}
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MOZ_ALWAYS_INLINE __m128i avg_sse2_4x2_4x1(__m128i a, __m128i b)
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{
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return _mm_not_si128(_mm_avg_epu8(_mm_not_si128(a), _mm_not_si128(b)));
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}
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MOZ_ALWAYS_INLINE __m128i avg_sse2_8x1_4x1(__m128i a, __m128i b)
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{
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__m128i t = _mm_castps_si128(_mm_shuffle_ps(_mm_castsi128_ps(a), _mm_castsi128_ps(b), _MM_SHUFFLE(3, 1, 3, 1)));
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b = _mm_castps_si128(_mm_shuffle_ps(_mm_castsi128_ps(a), _mm_castsi128_ps(b), _MM_SHUFFLE(2, 0, 2, 0)));
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a = t;
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return _mm_not_si128(_mm_avg_epu8(_mm_not_si128(a), _mm_not_si128(b)));
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}
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MOZ_ALWAYS_INLINE uint32_t Avg2x2(uint32_t a, uint32_t b, uint32_t c, uint32_t d)
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{
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uint32_t sum = a ^ b ^ c;
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uint32_t carry = (a & b) | (a & c) | (b & c);
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uint32_t mask = 0xfefefefe;
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// Not having a byte based average instruction means we should mask to avoid
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// underflow.
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sum = (((sum ^ d) & mask) >> 1) + (sum & d);
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return (((sum ^ carry) & mask) >> 1) + (sum & carry);
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}
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// Simple 2 pixel average version of the function above.
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MOZ_ALWAYS_INLINE uint32_t Avg2(uint32_t a, uint32_t b)
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{
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uint32_t sum = a ^ b;
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uint32_t carry = (a & b);
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uint32_t mask = 0xfefefefe;
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return ((sum & mask) >> 1) + carry;
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}
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namespace mozilla {
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namespace gfx {
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void
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ImageHalfScaler::HalfImage2D_SSE2(uint8_t *aSource, int32_t aSourceStride,
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const IntSize &aSourceSize, uint8_t *aDest,
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uint32_t aDestStride)
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{
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const int Bpp = 4;
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for (int y = 0; y < aSourceSize.height; y += 2) {
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__m128i *storage = (__m128i*)(aDest + (y / 2) * aDestStride);
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int x = 0;
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// Run a loop depending on alignment.
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if (!(uintptr_t(aSource + (y * aSourceStride)) % 16) &&
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!(uintptr_t(aSource + ((y + 1) * aSourceStride)) % 16)) {
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for (; x < (aSourceSize.width - 7); x += 8) {
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__m128i *upperRow = (__m128i*)(aSource + (y * aSourceStride + x * Bpp));
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__m128i *lowerRow = (__m128i*)(aSource + ((y + 1) * aSourceStride + x * Bpp));
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__m128i a = _mm_load_si128(upperRow);
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__m128i b = _mm_load_si128(upperRow + 1);
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__m128i c = _mm_load_si128(lowerRow);
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__m128i d = _mm_load_si128(lowerRow + 1);
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*storage++ = avg_sse2_8x2(&a, &b, &c, &d);
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}
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} else if (!(uintptr_t(aSource + (y * aSourceStride)) % 16)) {
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for (; x < (aSourceSize.width - 7); x += 8) {
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__m128i *upperRow = (__m128i*)(aSource + (y * aSourceStride + x * Bpp));
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__m128i *lowerRow = (__m128i*)(aSource + ((y + 1) * aSourceStride + x * Bpp));
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__m128i a = _mm_load_si128(upperRow);
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__m128i b = _mm_load_si128(upperRow + 1);
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__m128i c = loadUnaligned128(lowerRow);
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__m128i d = loadUnaligned128(lowerRow + 1);
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*storage++ = avg_sse2_8x2(&a, &b, &c, &d);
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}
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} else if (!(uintptr_t(aSource + ((y + 1) * aSourceStride)) % 16)) {
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for (; x < (aSourceSize.width - 7); x += 8) {
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__m128i *upperRow = (__m128i*)(aSource + (y * aSourceStride + x * Bpp));
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__m128i *lowerRow = (__m128i*)(aSource + ((y + 1) * aSourceStride + x * Bpp));
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__m128i a = loadUnaligned128((__m128i*)upperRow);
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__m128i b = loadUnaligned128((__m128i*)upperRow + 1);
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__m128i c = _mm_load_si128((__m128i*)lowerRow);
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__m128i d = _mm_load_si128((__m128i*)lowerRow + 1);
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*storage++ = avg_sse2_8x2(&a, &b, &c, &d);
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}
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} else {
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for (; x < (aSourceSize.width - 7); x += 8) {
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__m128i *upperRow = (__m128i*)(aSource + (y * aSourceStride + x * Bpp));
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__m128i *lowerRow = (__m128i*)(aSource + ((y + 1) * aSourceStride + x * Bpp));
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__m128i a = loadUnaligned128(upperRow);
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__m128i b = loadUnaligned128(upperRow + 1);
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__m128i c = loadUnaligned128(lowerRow);
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__m128i d = loadUnaligned128(lowerRow + 1);
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*storage++ = avg_sse2_8x2(&a, &b, &c, &d);
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}
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}
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uint32_t *unalignedStorage = (uint32_t*)storage;
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// Take care of the final pixels, we know there's an even number of pixels
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// in the source rectangle. We use a 2x2 'simd' implementation for this.
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//
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// Potentially we only have to do this in the last row since overflowing
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// 8 pixels in an earlier row would appear to be harmless as it doesn't
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// touch invalid memory. Even when reading and writing to the same surface.
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// in practice we only do this when doing an additional downscale pass, and
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// in this situation we have unused stride to write into harmlessly.
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// I do not believe the additional code complexity would be worth it though.
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for (; x < aSourceSize.width; x += 2) {
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uint8_t *upperRow = aSource + (y * aSourceStride + x * Bpp);
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uint8_t *lowerRow = aSource + ((y + 1) * aSourceStride + x * Bpp);
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*unalignedStorage++ = Avg2x2(*(uint32_t*)upperRow, *((uint32_t*)upperRow + 1),
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*(uint32_t*)lowerRow, *((uint32_t*)lowerRow + 1));
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}
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}
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}
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void
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ImageHalfScaler::HalfImageVertical_SSE2(uint8_t *aSource, int32_t aSourceStride,
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const IntSize &aSourceSize, uint8_t *aDest,
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uint32_t aDestStride)
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{
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for (int y = 0; y < aSourceSize.height; y += 2) {
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__m128i *storage = (__m128i*)(aDest + (y / 2) * aDestStride);
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int x = 0;
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// Run a loop depending on alignment.
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if (!(uintptr_t(aSource + (y * aSourceStride)) % 16) &&
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!(uintptr_t(aSource + ((y + 1) * aSourceStride)) % 16)) {
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for (; x < (aSourceSize.width - 3); x += 4) {
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uint8_t *upperRow = aSource + (y * aSourceStride + x * 4);
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uint8_t *lowerRow = aSource + ((y + 1) * aSourceStride + x * 4);
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__m128i a = _mm_load_si128((__m128i*)upperRow);
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__m128i b = _mm_load_si128((__m128i*)lowerRow);
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*storage++ = avg_sse2_4x2_4x1(a, b);
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}
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} else if (!(uintptr_t(aSource + (y * aSourceStride)) % 16)) {
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// This line doesn't align well.
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for (; x < (aSourceSize.width - 3); x += 4) {
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uint8_t *upperRow = aSource + (y * aSourceStride + x * 4);
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uint8_t *lowerRow = aSource + ((y + 1) * aSourceStride + x * 4);
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__m128i a = _mm_load_si128((__m128i*)upperRow);
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__m128i b = loadUnaligned128((__m128i*)lowerRow);
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*storage++ = avg_sse2_4x2_4x1(a, b);
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}
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} else if (!(uintptr_t(aSource + ((y + 1) * aSourceStride)) % 16)) {
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for (; x < (aSourceSize.width - 3); x += 4) {
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uint8_t *upperRow = aSource + (y * aSourceStride + x * 4);
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uint8_t *lowerRow = aSource + ((y + 1) * aSourceStride + x * 4);
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__m128i a = loadUnaligned128((__m128i*)upperRow);
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__m128i b = _mm_load_si128((__m128i*)lowerRow);
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*storage++ = avg_sse2_4x2_4x1(a, b);
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}
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} else {
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for (; x < (aSourceSize.width - 3); x += 4) {
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uint8_t *upperRow = aSource + (y * aSourceStride + x * 4);
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uint8_t *lowerRow = aSource + ((y + 1) * aSourceStride + x * 4);
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__m128i a = loadUnaligned128((__m128i*)upperRow);
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__m128i b = loadUnaligned128((__m128i*)lowerRow);
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*storage++ = avg_sse2_4x2_4x1(a, b);
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}
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}
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uint32_t *unalignedStorage = (uint32_t*)storage;
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// Take care of the final pixels, we know there's an even number of pixels
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// in the source rectangle.
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//
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// Similar overflow considerations are valid as in the previous function.
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for (; x < aSourceSize.width; x++) {
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uint8_t *upperRow = aSource + (y * aSourceStride + x * 4);
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uint8_t *lowerRow = aSource + ((y + 1) * aSourceStride + x * 4);
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*unalignedStorage++ = Avg2(*(uint32_t*)upperRow, *(uint32_t*)lowerRow);
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}
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}
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}
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void
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ImageHalfScaler::HalfImageHorizontal_SSE2(uint8_t *aSource, int32_t aSourceStride,
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const IntSize &aSourceSize, uint8_t *aDest,
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uint32_t aDestStride)
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{
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for (int y = 0; y < aSourceSize.height; y++) {
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__m128i *storage = (__m128i*)(aDest + (y * aDestStride));
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int x = 0;
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// Run a loop depending on alignment.
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if (!(uintptr_t(aSource + (y * aSourceStride)) % 16)) {
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for (; x < (aSourceSize.width - 7); x += 8) {
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__m128i* pixels = (__m128i*)(aSource + (y * aSourceStride + x * 4));
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__m128i a = _mm_load_si128(pixels);
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__m128i b = _mm_load_si128(pixels + 1);
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*storage++ = avg_sse2_8x1_4x1(a, b);
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}
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} else {
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for (; x < (aSourceSize.width - 7); x += 8) {
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__m128i* pixels = (__m128i*)(aSource + (y * aSourceStride + x * 4));
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__m128i a = loadUnaligned128(pixels);
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__m128i b = loadUnaligned128(pixels + 1);
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*storage++ = avg_sse2_8x1_4x1(a, b);
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}
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}
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uint32_t *unalignedStorage = (uint32_t*)storage;
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// Take care of the final pixels, we know there's an even number of pixels
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// in the source rectangle.
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//
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// Similar overflow considerations are valid as in the previous function.
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for (; x < aSourceSize.width; x += 2) {
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uint32_t *pixels = (uint32_t*)(aSource + (y * aSourceStride + x * 4));
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*unalignedStorage++ = Avg2(*pixels, *(pixels + 1));
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}
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}
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}
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} // namespace gfx
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} // namespace mozilla
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